WDM

BASICS

introduction
• Network generations: g • First: those which use copper‐based or microwaves, e.g. Ethernet, satellite, . . microwaves e g Ethernet satellite • Second: those in which copper is replaced by fiber such that data transmission is performed fiber such that data transmission is performed in optical domain, but data switching is done in electronic domain electronic domain • Third: WDM, data switching and transmission done in optical domain d i ti l d i

0.Optical carriers
• Normal: an optical carrier ( THz ) is used to p g handle traffic at some Gbps rates.4 nm )
. using wave modulation • Bit rate can be increased with several carrier Bit rate can be increased with several carrier waves propagating without significant interaction on the same cable: WDM ( FDM: h bl ( for very close frequency spacing.

one per direction
. so a fiber per direction
• Bi‐directional
– no need for two fibers. a fiber per direction the fiber. so. the wavelengths are split into two separate bands.DWDM implementations
• Unidirectional
– all wavelengths travel in the same direction within the fiber.

similar to the data side of a CD p – Separates different wavelengths into different angles g
. contains a mirror like device that works like a prism.Components (3) Components (3)
• Mux
– simple coupler combines all inputs into one output fiber
• Demux
– complex.